On 2021/9/13 上午11:00, 王贇 wrote: > > > On 2021/9/10 下午11:38, Peter Zijlstra wrote: >> On Thu, Sep 09, 2021 at 11:13:21AM +0800, 王贇 wrote: >>> When running with ftrace function enabled, we observed panic >>> as below: >>> >>> traps: PANIC: double fault, error_code: 0x0 >>> [snip] >>> RIP: 0010:perf_swevent_get_recursion_context+0x0/0x70 >>> [snip] >>> Call Trace: >>> <NMI> >>> perf_trace_buf_alloc+0x26/0xd0 >>> perf_ftrace_function_call+0x18f/0x2e0 >>> kernelmode_fixup_or_oops+0x5/0x120 >>> __bad_area_nosemaphore+0x1b8/0x280 >>> do_user_addr_fault+0x410/0x920 >>> exc_page_fault+0x92/0x300 >>> asm_exc_page_fault+0x1e/0x30 >>> RIP: 0010:__get_user_nocheck_8+0x6/0x13 >>> perf_callchain_user+0x266/0x2f0 >>> get_perf_callchain+0x194/0x210 >>> perf_callchain+0xa3/0xc0 >>> perf_prepare_sample+0xa5/0xa60 >>> perf_event_output_forward+0x7b/0x1b0 >>> __perf_event_overflow+0x67/0x120 >>> perf_swevent_overflow+0xcb/0x110 >>> perf_swevent_event+0xb0/0xf0 >>> perf_tp_event+0x292/0x410 >>> perf_trace_run_bpf_submit+0x87/0xc0 >>> perf_trace_lock_acquire+0x12b/0x170 >>> lock_acquire+0x1bf/0x2e0 >>> perf_output_begin+0x70/0x4b0 >>> perf_log_throttle+0xe2/0x1a0 >>> perf_event_nmi_handler+0x30/0x50 >>> nmi_handle+0xba/0x2a0 >>> default_do_nmi+0x45/0xf0 >>> exc_nmi+0x155/0x170 >>> end_repeat_nmi+0x16/0x55 >> >> kernel/events/Makefile has: >> >> ifdef CONFIG_FUNCTION_TRACER >> CFLAGS_REMOVE_core.o = $(CC_FLAGS_FTRACE) >> endif >> >> Which, afaict, should avoid the above, no? > > I'm afraid it's not working for this case, the > start point of tracing is at lock_acquire() which > is not from 'kernel/events/core', the following PF > related function are also not from 'core', prevent > ftrace on 'core' can't prevent this from happen... By a second thinking, I think you're right about the way it should be fixed, since disabling ftrace on 'arch/x86/mm/fault.c' could also fix the problem. Will send a formal patch later :-) Regards, Michael Wang > > Regards, > Michael Wang > >>
